The invention generally relates to an apparatus for thermally protecting transported freight, and more particularly to an insulated freight cover.
The ability to preserve the quality of temperature-sensitive items, by maintaining temperature within certain parameters, greatly increases the practicality and efficacy of transporting such goods by rail, by road or overseas. In furtherance of this ability, thermally protective freight covers have been employed to significantly insulate the temperature-sensitive goods from the environment at large.
Freight covers are designed to maintain the temperature of goods underneath them by inhibiting heat transfer to and from the goods by completely covering the goods with an insulated cover. When used in a container, freight covers typically are placed over the top of goods, and may extend downward to cover the front and rear of the load as well as the top. The cover preferably will fit flush against the side walls of the container at the level of the top of the goods. This configuration substantially isolates the freight underneath the cover from the air above the cover inside the container. Thus, while the air above the cover is subject to significant temperature fluctuations from environmental conditions, the freight below the cover is substantially thermally protected.
Of course, the effectiveness of such freight covers depends on a large number of variables. With respect to the goods themselves, temperature capacity is a major factor, but product density, load configuration and packaging also affect the operation of the cover. Another factor is the tightness of the fit of the cover around the goods, and the corresponding rate of air mixture from below and above the cover. To the extent that temperature transfer rates are generally related to the difference in temperatures between two mediums, the environmental conditions are also very relevant.
While the potentially pronounced effect of environmental temperature deviations is obvious, other environmental parameters also contribute significantly to the effectiveness of freight covers. Air flow patterns around the cover resulting from the design and velocity of the transport vehicle may further encourage such mixing, decreasing the effectiveness of the freight cover. Thus, there is a need for an insulated freight cover which reduces the effect of these variables.
One problem with some freight covers has been the difficulty of application of the covers. Due to their size and weight, the covers are typically rather heavy, and they are typically applied over a large area in confined quarters. Thus, effective application of a cover may be quite onerous. Because the cover may catch on freight during application or due to gaps in the freight configuration, the cover may tend to sag or bunch in certain areas, making it difficult to cover the entire load and maintain an effective seal.
Another problem is the sagging of the cover in transit due to the loading configuration, which may leave part of the load uncovered. In a typical loading configuration where a freight cover may be used, a container has two rows of paired pallet loads extending the length of the container. One row of pallets is placed against each side wall, and a center void is formed. Alternatively, a side gap or a number of side gaps may be formed if the pallets are adjacent and pushed flush against a side wall.
Where a center void exists, covers tend to be pulled by their own weight into the center void, receding the cover edges away from the sides of the container and permitting air from above the cover to mix more readily with the ambient air below. This type of problem is particularly likely to occur in regions where the cover has bunched.
Where a side gap is present, the cover is higher near one side wall than near the other, and gravity combined with the natural transport movements of the container tend to cause the cover to slide laterally downward toward the lower side, receding from the opposite side wall.
Thus, it is desirable for a cover to be easily applied and to be resistant to receding from the side walls of the container.